GABA shunt metabolites and enzymes have been measured in mouse brain and glial and neuronal cells in culture. GABA concentrations in brain and cultured glioma cells are comparable, whereas the neuroblastoma cells contain one-tenth as much. In general, the enzyme activities measured, GABA tranaminase, succinic semialdehyde dehydrogenase and glutamate dehydrogenase are much lower in the cultured cells, and GABA transaminase is absent from the glial cells. The anticonvulsant drugs, aminooxyacetate (AOA) and dipropylacetate (DPA), elevated GABA concentrations in mouse brain and neuroblastoma cells. Only DPA affected the concentrations of GABA in glioma cells. The convulsant drug, isoniazid, depresses GABA levels in brain, had no effect in glioma cells and increased GABA in the neuroblastoma cells.